Thanks for the upload. Here are some observations.
Your site has Query Monitor activated. That’s not a good idea in production, because it imposes some overhead. Deactivate Query Monitor in production.
Your site has 401K posts and 86K users. Yet your MariaDB RDBMS instance is only configured for 128MiB of innodb buffer pool space. You’ll see some improvement if you can add buffer pool space. If I were you I’d try to bump it up to at least 512MiB.
In your 60-sec monitor, most queries are just fine. There are just two slow ones. One is from the FooEvents plugin, rendering something in the backend. I don’t know enough about that plugin to offer any suggestions.
The other is from the Users -> All Users display, which has inefficient queries for user roles. That inefficiency only shows itself with large numbers of users. I have a plugin, Index WP Users For Speed, to remediate that.
You seem to be using a persistent object cache. That’s good (but I can’t tell which cache type –redis, memcached, sqlite, whatever — from your uploaded data).
I hope this helps.
